The invention relates to a gas-discharge lamp, in particular a deuterium lamp, having a housing base made of an insulating material.
In the deuterium lamps used most often today, the cathode is surrounded by a metal housing, which lies at the same potential as the anode space and the molded body. This results in secondary discharges developing, which lead to metal-coating in the case of translucent lamps. The secondary discharge has the further effect that molded body erosion takes place and the intensity of the lamp decreases, because the discharge current can no longer flow completely through the molded body.
In the known deuterium lamps the housing consists of a total of six parts, which all carry tolerances and must be welded to each other. Because the tolerances add up independently, the spread in standard factory models is disproportionately large, especially in the front housing part. Such deuterium lamps further require a high expenditure of time for the assembly. Here, both the front and also the rear housing part are made of metal, wherein the two housing parts are usually connected by a metallic intermediate wall. The cathode is surrounded by the housing front and the cathode window, which are mounted on the intermediate wall. The cathode window and the molded body are thus connected to each other in a conductive way due to the construction. This allows the molded body and the cathode window to lie at the same potential which is lower, however, than the plasma potential at the location of the molded body. This has the result that positive ions are accelerated from the plasma onto the molded body and contribute to its abrasion. Through this form of sputtering, the diameter of the aperture increases and the electrode density in the aperture decreases, whereby the lamp loses UV intensity and the abraded material of the molded body settles on the inside of the bulb and thus results in a reduction of the intensity of the lamp.
German published patent application DE 199 01 919 A1 describes a miniature deuterium arc lamp. The deuterium arc lamp has a construction that is mounted on the distal end of the electrical conductor in an elongated glass bulb at a spacing from the glass bulb, wherein the spacer devices, which engage with the configuration and are arranged at a small distance relative to the bulb, are provided for limiting the transverse movement of the construction in the bulb. Here, the anode is arranged transverse by a dielectric lying in-between at a spacing from a conductive sheet.
Spacer devices fix the anode, the conductive sheet, and the dielectric lying in-between, which were installed in a self-supporting manner on the end of the conductor in previously known deuterium lamps.
European patent application publication EP 0 727 810 A2 describes a gas-discharge tube having a focusing support element of an insulator, wherein the focusing electrode support element has a front surface and a rear surface opposite the front surface, with a thermionic cathode for the emission of thermionic electrons, wherein the cathode is located on the front surface side of the focusing electrode support element; an anode for receiving the thermionic electrons, which the thermionic cathode emits, wherein the anode is located on the rear surface side of the focusing electrode support element and is opposite an opening of the passage hole; a focusing electrode supported by the focusing electrode support element, which is provided by a focusing opening located at a position of an opening of the passage hole for convergence paths of the thermionic electrodes; a spacer between the focusing electrode support element and the anode, which contacts both the rear surface of the focusing electrode support element and also a front surface of the anode; and an anode support element of an insulator, wherein the anode support element is located on an opposite side of the focusing electrode support element by the anode and has a surface that contacts the rear surface of the anode, in order to push the anode onto the rear surface of the focusing electrode support element by the spacer, whereby an interval is fixed between the focusing electrode and the anode of the electrode support element and the spacer.
When a discharge occurs in such a gas-discharge tube among the thermionic cathode, the focusing electrode, and the anode, the anode generates heat after receiving the thermionic electrons, and the focusing electrode also generates heat after bombardment with cations.
German published patent application DE 11 2005 001 775 describes a gas-discharge tube in which a sealed container, an anode and a cathode are provided, and a conductive part that limits a discharge path, wherein the conductive part is arranged between the anode and the cathode and reduces the discharge path formed between the anode and the cathode. Furthermore, the gas-discharge tube has a cathode cover, which is made of ceramic and encloses the cathode. In this gas-discharge tube, as in DE 11 2005 001 775, the cathode cover is encased by the cathode-side cover section, in which only the slot for the emission of electrons is provided as the necessary minimal opening. In this way, the heat-retention effect of the cathode is remarkably maintained by the cathode-side cover section, and the energy consumption is reduced. The ceramic housing thus serves for maintaining the heat within the cathode space.
The discharge lamps described here have the consequence, among other things, that secondary discharges arise, and thus molded body erosion takes place on the aperture. This has the result that the intensity and the service life of the gas-discharge lamp are significantly reduced. Furthermore, the discharge lamps described above are complicated in their assembly.